The present disclosure relates to a syringe barrel and a pre-filled syringe.
One type of known conventional syringe is a pre-filled syringe that has previously been filled with a liquid drug or the like (see, for example, JP 11-501597 T and Japanese Patent No. 4156791). It is important that the liquid drug or the like contained in the pre-filled syringe is prevented from leaking through a distal end opening of the syringe before its use, particularly during transport. Therefore, a cap is attached to the syringe barrel of the pre-filled syringe to seal the cylinder tip (syringe distal end opening) of the main body of the barrel in a liquid-tight manner.
A known structure for attaching the cap to the cylinder tip is one in which the cap is attached to the cylinder tip only by threaded engagement to seal a nozzle tip in a liquid-tight manner (see, for example, JP 11-501597 T). However, in a case where the cap is attached to the cylinder tip only by threaded engagement, there is a fear that the threaded engagement is loosened by vibration or the like during transport so that leakage of the liquid drug or the like contained in the syringe occurs.
For this reason, a structure for preventing the loosening of the cap is disclosed in which (i) a projection (inward projection) that projects inward from the inner periphery of the cap and (ii) a projection (outward projection) that projects outward from the outer periphery of the cylinder tip to be engaged with the inward projection, are engaged with each other to increase the rotational resistance of the cap against the cylinder tip (see, for example, Japanese Patent No. 4156791).